1. Field of the Invention
The present invention relates to precursor compositions that are useful for forming tantalum-containing films, e.g., by chemical vapor deposition (CVD) or atomic layer deposition (ALD), as well as to tantalum-containing barrier layers or films and to copper-metallized semiconductor device structures including tantalum-containing layers or films.
2. Description of the Related Art
In the field of semiconductor manufacturing, copper (Cu) and low k dielectrics are being increasingly employed in high performance silicon integrated circuits. Since Cu is very mobile in silicon (Si) and silicon dioxide (SiO2), effective diffusion barriers against Cu migration are required for the use of Cu metallization, inasmuch as the copper/interlayer dielectric interface determines the stability and reliability of the metallization scheme.
A variety of refractory metals, refractory metal nitrides, and metal-silicon-nitrogen compounds have been intensively investigated for use as barrier material. See, for example, U.S. Pat. No. 6,951,804 to Seutter et al. and U.S. Pat. No. 6,960,675 to Chen et al. Each of these U.S. patents is incorporated herein by reference in their entirety.
Among such materials, tantalum (Ta) and tantalum nitrides (TaN) are considered to be among the most promising candidates because of their stability under high temperature, high degree of adhesion, low resistivity, uniformity of their films and their inertness towards Cu.
As the size of the pattern shrinks and the aspect ratio increases, vapor deposition techniques, e.g., chemical vapor deposition (CVD), atomic layer deposition (ALD), digital CVD, pulsed CVD, or the like, are necessary to deposit the barrier layer, in order to minimize barrier layer thickness while achieving effective barrier properties.
Against this background of continuous shrinkage in feature size and progressive increase in aspect ratio, chemical vapor deposition (CVD) and atomic layer deposition (ALD) are increasingly preferred for depositing thin, conformal and smooth barrier layers in vias and trenches. For such applications, suitable tantalum precursors are required for forming tantalum-containing barrier material on substrates.
From a practical standpoint, Ta amides, such as, PDMAT [Ta(NMe2)5], and PEMAT [Ta(NEtMe)5] and Ta imides, such as, TBTDET [t-BuN═Ta(NEt2)3], and TAIMATA [t-AmN═Ta(NMe2)3] represent some currently available TaN precursors. Thermal stability of amides is problematic. For example, PDMAT is a solid with a melting point of 167° C. However, PDMAT decomposes at temperatures above 80° C. PEMAT is a low melting point solid. PEMAT also decomposes at temperatures above 80° C.
There is a continuing need in the art for tantalum precursors useful for deposition applications, e.g., to form copper migration barrier structures.
In current practice, copper migration barrier structures are formed by reactive sputter deposition of a TaN layer onto a patterned, nominally dense dielectric, followed by sputter deposition of Ta metal prior to sputter deposition of a copper seed layer.
There is correspondingly a need for barrier layers, e.g., for copper metallization of semiconductor device structures, that do not introduce nitrogen to the underlying dielectric film.